Question about 1994 GMC Safari

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I have a 1994 gmc safari.It seems to have a smooth idle at times

The engine goes from smooth idle to small rough idle.I have replaced fuel pump,plugs and wires,most sensors,adjusted timing,filters. The engine will run real smooth for one day,rough the next. (please help)

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  • Anonymous Mar 21, 2014

    service engine soon light is on. engine runs a bit rough at idle with a/c onhad pepboy hook up scan tool code was for mass air flow sensor



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Im not sure if you got it fixed yet! It could possibly be idle air control valve. But here some more suggestions! I had a 94 Safari van 4.3 liter I was working on for about three days and I finally figured out what was wrong with it. It would run fine for a couple minutes and as soon as I hit the gas and let off it would surge, but anyways I ended up changing the distributer, after the fuel pump and filter, mass air flow sensor, egr valve, idle air control valve, map sensor, and ignition module. So that might sove the problem if you were on the same track with it as I was. Hope this helps ya!

Posted on Mar 09, 2009

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You want to charge me for your help,but if i fix it myself you want me to tell you how i cured the thanks,but i will give you the info for a price

Posted on Mar 03, 2009


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2000 hyundai lantra sportswagon running rough, idling rough also, when accelerating splutters/spurges. Thinking maybe spark plugs or timing belt??

Needs a tune up. Adjust engine timing, replace plugs and plug wires, replace air filter, oil and oil filter, fuel filter and clean fuel injectors, adjust valves.

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Rough idle in drive, correct rpm

Car idle is rough Inspection Service & Cost A rough idling engine can be caused by a number of issues, some of them are serious while others tend to be minor, but the symptoms remain pretty much the same. The car will feel rough and bouncy when the engine is running. The car will also idle below its regular speed, display inconsistent RPMs and may produce a shaking, skipping or slipping sound when the vehicle is running.
While a rough idling engine may seem to be a simple inconvenience it often indicates a deeper problem within the engine. The vehicle should be inspected and repaired as soon as possible because small problems have a way of turning into expensive repairs. How this system works: The idle speed of an engine is basically the rotational speed the engine runs on when it is un-coupled from the drivetrain and the throttle pedal is not being depressed. The idle speed is measured in the revolutions per minute of the crankshaft.
When an engine is running at idle speed it generates enough power to smoothly operate equipment such as the water pump, alternator, and power steering but not enough power to move the vehicle itself. A passenger car will usually idle between 600 RPMs and 1000 RPMs. A properly functioning idle should run smoothly without skipping or slipping. Common reasons for this to happen:
  • Dirty Fuel Injectors: The fuel injection system injects fuel into the cylinders, which creates a mix of air, and fuel to ignite and burn. Fuel injectors have tiny nozzles to spray the fuel into the cylinder and they can become clogged over time. clogged or failing fuel injector creates a lack of fuel in the vehicle's engine. This can cause a rough idle, it can also cause symptoms such as slow acceleration or the car not feeling as if it has enough power. If the problem is addressed early, it is possible to clean the injectors, which will restore them to full function. If this condition is not addressed in a timely manner the injectors will need to be replaced. Incorrect Idle Speed: While the average idle speed falls between 600 to 1,000 RPMs, if your vehicle is experiencing a rough idle it could be due to an incorrect idle speed setting. A trained mechanic can easily adjust the idle speed, and it should stay at the proper speed. If an adjusted idle speed becomes inconsistent or changes at random intervals there may be a bigger problem that needs to be explored. Vacuum Leak: If the vacuum system has a leak, it can seriously affect the ability of the vehicle's computer to regulate the air to fuel ratio. This can lead to a rough idle and if the problem is not addressed the car may experience slow acceleration and a lack of power. Vacuum leaks should be inspected and repaired immediately. Incorrectly Installed or Damaged Plugs: Spark plugs are responsible for creating the spark that allows the vehicle to burn fuel. If spark plugs are improperly installed or malfunctioning, the idle speed can be affected. The vehicle's engine may vibrate or there may be slipping or straining sounds coming from the engine. Defective or Clogged Fuel Pump: A rough idle can be related to fuel delivery issues. The fuel pump, which is responsible for pulling fuel from the gas tank to the fuel injectors, can become clogged or defective. If this happens the engine will not get enough fuel, which can cause a rough idle, sputtering, stalling and even slow acceleration. Clogged Fuel Filter: A clogged fuel filter can cause similar problems. The job of the fuel filter is to screen out contaminants in the fuel, over time it will become clogged and need to be replaced. A rough idle is one symptom of a clogged fuel filter. Failing Electrical Components: A problem or failure in the ignition system or various electronic components can cause a rough idle. If this is the case, the problem will usually get worse as RPMs increase. Common culprits include the ignition control module, plug wires, coils, and spark plugs. Defective Airflow Sensor: A defective airflow sensor can be responsible for a rough idle. A mass airflow sensor detects the amount of air coming into the fuel injection system and sends that information to the vehicle's computer. The computer uses that data to deliver the proper amount of fuel to the air in the vehicle. Over time these sensors can malfunction or become dirty. One of the first symptoms of a malfunctioning airflow sensor is a rough idle. The car may also accelerate slowly and even stutter or stall as the problem progresses. Dirty Oxygen Sensor: Oxygen sensors measure how rich or lean the gases are as they exit the combustion chamber. Depending on the results, the amount of fuel entering the engine is adjusted by the vehicle computer. The ultimate goal is to maintain an ideal mixture that produces the lowest emissions. A dirty or failing oxygen sensor will usually trigger the check engine light and can lead to a rough idle, lower fuel efficiency and failed emission test.

Sep 28, 2016 | AC Cars & Trucks

1 Answer

My 2000GMC Safari after driving for about 5 miles will start to misfire and when i stop at an intersection the engine will idle rough then smoothing out

Start with the basics.
Check the following:
Air filter, spark plugs and high tension leads, fuel filter, all under-hood levels.

Oct 11, 2014 | 2000 GMC Safari

1 Answer

Running rough-1987 Ford Ranger 2.3 L 4 cyl. Had been running very smoothly until 2 weeks ago when it began backfiring and running rough, especially at low speeds, without my having made any adjustmen

If your car has a mas air flow sensor (usualy located right aroung air filter or in air passage after the air filter) check and clean the sensor. This looks like a small spring on the end of 2 wires. BE CAREFUL not to damage the sensor. I have seen where the sensor gets dirty over time and this can cause a rough idle.

Jul 11, 2012 | Cars & Trucks

1 Answer

Really rough engine idle at cold start up,, reving the engine seems to smooth it out,,,,

Some causes about rought idle could be:
- Valve adjustment
- Incorrect ignition timing,
- Vacuum leaks
- Bad ignition wires (Test w/ ohmmeter)
- Incorrect idle speed
- Cold Start Injector always "ON" (Revised injector time switch avail.)

A source of rough idle in EFI engines is air leaks or vacum leaks these leaks will upset the fuel mixture without triggering any codes. A bad oxigen sensor will also cause a rough idle, but you should see a code for it ( I think is number 5, but check it).

A good place to start would be an inspection of the spark plugs, plug wires, ignition timing, and idle speed. Next would be valve adjustment. Don't overlook the simple things.

Hope this helps, keep us updated and just keep in mind that your feedback is important and I'll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa.

Nov 04, 2011 | 1997 Honda Accord

1 Answer

I got a 1999 ford ranger with a 2.5l it runs smooth at idle, an runs smooth while drive but bad fuel economy. when u rev up at idle an let go of the throttle it runs rough an then smooths out. ive...

You have two coils on this engine. Test each wire for spark with the engine running. You'll find at least one wire not sparking. replace the coil that has the wire that's not sparking.

May 14, 2011 | Ford Ranger Cars & Trucks

1 Answer


on your discription,i would say someone has not replaced a vacum pipe under the bonnet,or placed the wrong vacum pipe on the wrong pipe if you know what i mean,the vacum pipes run around the engine small pipes if you pull one of you will hear a sucking noise or if you spit on your finger you should feel it ****.when you say it blew brake line what do you mean ,please tell me excatly what happened because this realy baffles me,please come back to me on this problem .adrian,,,,

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1 Answer

Gmc sonoma 4.3 1991 rough start up occasionally

check to see if your egr vave is sticking. if so you will need to replace it.

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